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https://issues.apache.org/jira/browse/CB-10774?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15266158#comment-15266158
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Torsten Freyhall commented on CB-10774:
---------------------------------------
In my opinion, the javascript code fixed in #CB-10530 should never execute
unless the command bridge (I think it was called something like that) has
changed.
My quick tests pointed at that the reason for the bridge change detection
timeout to trigger in the javascript was that the native code expected the
javascript callbacks to be run async. I haven't dug any further into the issue,
just checked that this also solved the problem in #CB-10530. Also, it might
have other side effects, however they should be limited to the UIWebViewEngine,
since WKWebView performs javascript async by default.
> CDVUIWebView performs javascript synchronous, but command queue expects it to
> be async
> --------------------------------------------------------------------------------------
>
> Key: CB-10774
> URL: https://issues.apache.org/jira/browse/CB-10774
> Project: Apache Cordova
> Issue Type: Bug
> Components: iOS
> Affects Versions: 4.1.0
> Reporter: Torsten Freyhall
> Assignee: Shazron Abdullah
> Labels: cordova-ios-4.1.1
>
> From https://issues.apache.org/jira/browse/CB-10530 regarding app freezing at
> launch.
> ...
> However I was not sure about why the timer resolves due to long script
> execution times though. It seems like the intention is that whenever
> gap://ready is loaded in the iframe, the immediate response from the native
> side should be to call nativeFetchMessages() which should clear the timeout.
> Therefore I dug a little deeper in the native side, and found that the
> evaluateJavaScript:completionHandler: in CDVCommandQueue expects
> implementation to to be async (a comment in the code says so), but the
> CDVUIWebViewEngine method actually is implemented synchronous.
> I wrapped the entire method in a dispatch_async call (maybe a very naive
> solution, it might mess with references?):
> {code}
> dispatch_async(dispatch_get_main_queue(), ^{
> NSString* ret = [(UIWebView*)_engineWebView
> stringByEvaluatingJavaScriptFromString:javaScriptString];
> if (completionHandler)
> { completionHandler(ret, nil); }
> });
> {code}
> This also solves the original issue on cordova-ios 4.0.1 as the timeout never
> resolves, so maybe asyncing this method should also be a part of the proper
> fix?
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